This is adapted from a paper that was first turned in as a school assignment at ACHS.

Essential Oils Aren’t Oily

“What is an essential oil?” It seems like a pretty simple question — until you stop to think about it.  Essential oils are neither essential (necessary/critical) nor oily!  But that’s what the name sounds like.  So what in the world are they?

In a nutshell, an essential oil is comprised of the volatile (meaning it evaporates easily), non-water-soluble (doesn’t dissolve in water) aromatic (you can smell it) constituents of a plant. This essential oil is extracted from the plant material by distilling it with steam, or occasionally by expression (basically, squeezing it out).  Citrus oils are typically expressed.

“Real” Oils

Scientifically speaking, essential oils really are oils, but they aren’t the same as the category of substances we usually think of as oils, or refer to as “oils” in everyday language terms.  Officially, those are “fixed” oils, or base oils.  If you leave base oils exposed to the air, they will eventually turn rancid (some faster than others).  They feel oily and can even leave oily stains — as I’m sure some of you have experienced!  (Can you say “laundry challenge”?)

Essential oils are the opposite in all these ways.  If left out, they don’t turn rancid; they evaporate!  That’s why they’re called volatile.  (“Volatile oils” is the category that officially contrasts with “fixed oils.”)  Most do not feel oily.  The few that do feel slightly oily are still well short of the kind of oiliness you feel with a base oil.  And they do not leave oily stains behind.  They do dissolve in oil rather than water.

Essential Oils Aren’t Essential!

Essential, in this context, does not indicate critical or necessary. In fact, essential oils are created as a result of secondary processes within their respective plants. They are not imperative to the plant’s basic survival, and shouldn’t be confused with the sap. They do provide benefits to the plant – for instance, attracting beneficial insects or repelling harmful ones – but they aren’t part of the plant’s primary metabolism.

Essential here is used to indicate that the aromatic oil is the “essence” of a plant. Essence is a term created by Paracelsus, a medieval alchemist (Petersen, 2015, p. 19). It means “spirit,” and is used here to indicate that essential oil is viewed by many as the “spirit” or life force of the plant, and/or that it carries the fragrance representative of the plant’s unique quality or character.

In fact, essential oils (and similar substances) are sometimes (particularly in older literature) referred to merely as “essences.”  If you look at the first two definitions of essence at Dictionary.com, you get a pretty good picture of the word’s growth:

1. the basic, real, and invariable nature of a thing or its significant individual feature or features.

2. a substance obtained from a plant, drug, or the like, by distillation, infusion, etc., and containing its characteristic properties in concentrated form. (Dictionary.com, 2015)

So, then,  “essential” refers to the characteristic aroma of the oil and its source plant.  “Oil” relates to the substance’s solubility in oil rather than water.  And the final defining feature of essential oils is their volatility – that is, the fact that they evaporate readily.

References:

essence. (n.d.). Dictionary.com Unabridged. Retrieved May 21, 2015, from dictionary.reference.com/browse/essence

Petersen, D. (2015). AROMA 203: Aromatherapy I. Portland, OR: American College of Healthcare Sciences.